I read it as an example of natural selection. The natives who attune themselves to a particular risk, are much less like to die, and more likely to pass along, this particular idea.
Or.. humans in general have evolved the ability to gauge risk and modify their behavior accordingly, long before any humans stepped foot in Papua New Guinea. That this particular culture is more vigilant than others (if in fact that's the case, which I highly doubt) has nothing to do with natural selection. It has to do with culture.